1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device or the like. More particularly, the present invention relates to a method of processing a substrate using plasma.
2. Description of the Related Art
A semiconductor device is generally manufactured in part by forming a layer on a semiconductor substrate, forming an etching mask on the layer, and etching the layer through the etching mask to pattern the layer. Plasma is often used as the means to form such a layer on a substrate and/or to etch a layer formed on a substrate. In particular, plasma is widely used in the manufacturing of a semiconductor device wherein the design rule is less than about 0.13 μm.
A conventional process using plasma is carried out as follows. First, a semiconductor substrate is positioned in a chamber. Then, a bias power and a source power are applied to the chamber while a source gas is supplied into the chamber to generate the plasma. The semiconductor substrate is processed in the chamber using the plasma. Subsequently, the generating of the plasma is suspended, and a purge gas is supplied into the chamber to purge the chamber. Finally, the processed semiconductor substrate is unloaded from the chamber.
The semiconductor substrate is usually disposed on an electrostatic chuck (ESC) while is it being processed by the plasma. Direct current is supplied to the ESC to generate a Coulomb force that acts on the semiconductor substrate to attract the substrate to the ESC. After the plasma is extinguished, the current to the ESC is cut off. Accordingly, the semiconductor substrate is released from the ESC. At this time, the purge gas aids in discharging the semiconductor substrate.
Moreover, electrons having a high mobility frequently collide against particles in the plasma such that the particles acquire electric charges. However, the energy provided to the particles in the plasma is cut off once the plasma in the chamber is extinguished. Accordingly, the particles collect in regions adjacent the semiconductor substrate due to gravity and the Coulomb force acting on the semiconductor substrate. The particles act as contaminants. In particular, a great number of particles are present in the chamber when the semiconductor substrate is discharged by the purge gas and thus, the substrate is likely to become contaminated before it is unloaded from the chamber.
Methods for minimizing the number of particles remaining in the area adjacent the semiconductor substrate, after the substrate has been processed using a plasma, are disclosed in Korea Patent Laid-Open Publication No. 2004-22346, Japan Patent Laid-Open Publication No. 2003-100720, and U.S. Pat. No. 5,573,597 (issued to Lantsman). In a method disclosed in Korea Patent Laid-Open Publication No. 2004-22346, the processing chamber is purged using a gas that is excited by a high frequency power, once the plasma has been extinguished. However, it is still difficult using this technique to detach particles that are held to the semiconductor substrate by a Van der Waals force. In a method disclosed in Japan Patent Laid-Open Publication No. 2003-1000720, the contaminants are collected using a separate electrode provided in the processing chamber. However, the control and timing of the operation of the separate electrode render this method complicated. In a method disclosed in U.S. Pat. No. 5,573,597, once the generating of plasma is suspended, the bias power is controlled to create a repulsive force that prevents contaminants from accumulating on and around the semiconductor substrate. However, the repulsive force also acts to repel the semiconductor substrate to such an extent that the substrate may pop up off of the wafer chuck. As a result, the substrate can be damaged, especially by the member that is used to unload the substrate after it is processed.
Thus, damage to and failure of the semiconductor device due to contaminants, such as particulate contaminates, continue to frequently occur as the result of the processing of the substrate of the device using plasma.